The Coin Alert app is a Node.js application that tracks cryptocurrency prices and sends SMS alerts when a coin's price crosses a set threshold. The app uses Express, MongoDB, Twilio, and Agenda to retrieve data from the CoinMarketCap API, store it in a database, and schedule tasks to run at regular intervals. By following this tutorial, developers can create their own version of the Coin Alert app, which can help them stay informed about cryptocurrency prices without constantly checking the markets.